Odds converter: convert fractional, decimal and American odds

How an odds converter works

Odds are the price of a bet, and the same price can be written three ways. Fractional odds such as 5/2 are the British tradition. Decimal odds such as 3.50 are used in Europe and by betting exchanges. American odds such as +250 are used in the United States. The converter takes any of them and shows the others.

A price of 5/2 means a profit of five pounds for every two staked. In decimal, the same price is 3.50, which is the total return per pound including the stake. In American odds, a positive number is the profit on a hundred staked, so +250 is 250 on 100.

The converter also shows the implied probability, which is the chance the price suggests. It is one divided by the decimal odds, written as a percentage. A price of 2.00 implies fifty per cent.

Fractional to decimal odds converter

To turn fractional into decimal, divide the first number by the second and add one. 5/2 is 2.5 plus one, which is 3.50. 8/1 is 9.0. Evens, written 1/1, is 2.0. Short prices go the other way: 1/2 is 1.50.

To go from decimal to fractional, subtract one and write the result as a fraction. 3.50 minus one is 2.5, which is 5/2. Bookmakers use a limited set of traditional fractions such as 11/4 and 13/8, so a converted decimal is matched to the nearest familiar price.

Decimal and American odds converter

For decimal odds of 2.0 or more, the American figure is positive: take the decimal minus one and multiply by one hundred. 3.50 gives +250. Below 2.0 the American figure is negative: divide one hundred by the decimal minus one. 1.50 gives -200, which means you stake two hundred to win one hundred.

American odds are the standard for the major US sports, and UK bettors meet them on international markets and in articles from US publishers. The converter reads both signs. Type +150 or -200 and it shows the fractional and decimal equivalents.

Implied probability and the bookmaker’s margin

The implied probability of a price is what the price says about the chance of the outcome. At 4.0, or 3/1, the implied probability is twenty-five per cent. Add up the implied probabilities of every outcome in a market and the total comes to more than one hundred per cent. The excess is the bookmaker’s margin.

In a football match with prices of 2.10 for home, 3.40 for the draw and 3.60 for away, the implied probabilities are about 47.6, 29.4 and 27.8 per cent, which add up to about 104.8. The extra 4.8 is the overround. A bettor who wants the best price is looking for the market with the smallest overround.

Implied probability is not a forecast. It says how the market has priced the outcome, not how likely it is to happen. If your own view is that a team has a better chance than the price implies, that is a reason you might back it. If you have no view, the number gives you no edge.

Which odds format do UK bookmakers use?

UK bookmakers show fractional odds by default, particularly in racing, and most let you switch the whole site to decimal in the account settings. Betting exchanges and many comparison tools use decimal because the sums are easier: multiply the stake by the decimal odds to get the return.

Decimal makes comparison easier. If one bookmaker offers 11/4 and another 3.80, convert 11/4 to 3.75 and you can see at a glance which is bigger. The converter does that in one step.

Common prices worth knowing

A handful of prices come up all the time, and knowing their decimal and implied-probability equivalents helps you read a market quickly. Evens is 2.00 and fifty per cent. 2/1 is 3.00 and about thirty-three per cent. 4/1 is 5.00 and twenty per cent. 10/1 is 11.00 and about nine per cent. At the short end, 1/2 is 1.50 and sixty-seven per cent, and 1/4 is 1.25 and eighty per cent.

Notice the pattern. Fractions with a larger first number are longer shots. Prices below evens, where the second number is bigger, are favourites. Decimal odds below 2.00 and negative American odds are the same thing in different clothes.

Odds on betting exchanges and at bookmakers

Betting exchanges show decimal odds and let you back and lay. The price you see is set by other bettors, not by a bookmaker, and the exchange takes a commission on winnings. A bookmaker’s price has a margin built in. Comparing the two means converting to the same format first, which is where the converter helps.

Exchanges are outside what this site covers, and every operator we list is a licensed bookmaker. The point here is only that a decimal price on an exchange and a fractional price at a bookmaker are two ways of writing the same kind of number.

Odds in horse racing: board price and starting price

In racing, you will see an early or board price, and a starting price, or SP, which is the price at the off. If you take SP, you accept whatever it turns out to be. Converting the board price and the SP into decimal lets you see how far a price moved.

Racing odds are traditionally fractional, and unusual fractions such as 9/2, 11/4, 13/8 and 100/30 are standard. The converter reads all of them and shows the decimal. For each way bets the place part uses a fraction of the odds, and the each-way calculator works it out.

Boosted odds and what they change

A bookmaker may offer a boosted price on a selection, a higher price than the market. The conversion works the same way. Enter the boosted price and you can see the implied probability, and compare it with the original. A boost increases the return if the bet wins and does not change the chance that it does.

Boosts usually carry a maximum stake and an exclusion for some bet types, and some operators pay the extra in free-bet credit. Read the terms. Converting the odds is one step, and the conditions are the other.

Why the same price looks different on different bookmakers

Bookmakers set their own prices and margins, so the same team can be 2.10 at one and 2.00 at another. Over a season, small differences add up. A habit of comparing the price on the bet slip with another bookmaker takes less than a minute.

The converter lets you do that without translating in your head. If one operator quotes 11/4 and another 3.60, convert 11/4 to 3.75 and the first is the bigger price. The comparison has to be like for like, and a quick conversion is the only way to be sure.

Remember that a better price is not a better bet. It is a better price on the same bet.

Using the converter with other calculators

Once the odds are in the format you want, take them to the other tools. The accumulator calculator multiplies the odds of several selections, and the each-way calculator splits a bet into win and place parts. For the bookmakers that offer a given feature, see the main comparison, the horse racing page or the football page.

GambleAware gives free, confidential support, and GamStop blocks access to every licensed UK online gambling site for a period you choose. Both are linked in the footer of every page. Betting is for people aged 18 and over.

As a decimal odds converter it turns 5/2 into 3.5. As an American odds converter it reads +250 as 3.5 and -200 as 1.5. A betting odds converter helps when one bookmaker shows fractions and another site shows decimals, because the decimal odds converter and the American odds converter give the same price in a different notation. The odds converter above shows all three formats at once, so one odds converter replaces three separate lookups.